Satellites make much of modern warfare possible, through GPS systems, wireless communications and sophisticated weather forecasting. This makes satellites tempting military targets. The US Air Force is now responsible for defending American satellites and spacecraft and wants to continue to do so. But President Donald Trump says the perils require a new military branch, which has come to be known as the Space Force. Critics say this would just add bureaucracy and costs. Supporters say a new military branch is needed to prioritise US defenses for the next battlefront.

Is there a true military threat in space?

Yes, but not in the Hollywood sense of alien invaders attacking lower Manhattan. The main threat is the ability to disable or destroy an adversary’s satellites from the ground. In 2007, China first used a ballistic missile to destroy its own old weather satellite orbiting 535 miles (861 km) above Earth in 2007; Russia has been testing a missile that could be used to strike and destroy a satellite or ballistic missile. It’s likely that other nations won’t be far behind. If you destroy a spy satellite, the flow of real-time intelligence from a particular spot in China or Iran could stop. A communications satellite that’s jammed from the ground could mean ground troops suddenly find themselves operating blindly. And because existing international treaties governing space are unclear, even civilian satellites could be targeted by nations looking to contain or punish their enemies.

Was the Space Force Trump’s idea?

No, though he is the first president to publicly call for a separate military branch for space. The debate over space militarisation dates to at least the Cold War, when the US and Soviet Union first realised that controlling space could give them an edge in a conflict. In 1982, the investigative arm of Congress urged the creation of an “aerospace force” or “space force” to develop “laser battle stations in space” that could defend against a Soviet ballistic missile attack. The following year, President Ronald Reagan called for such a system, the Strategic Defense Initiative, which critics nicknamed “Star Wars.” (It never advanced beyond the research phase; its successor, the Missile Defense Agency, uses Earth-based systems like Thaad to destroy missiles at high altitudes.) In early 2001, a commission led by former Secretary of Defense Donald Rumsfeld concluded that the US wasn’t prepared to defend its enormous dependence on satellites. In 2017, House of Representatives members led by Representative Mike Rogers, an Alabama Republican, began pushing for a new “space corps”.

Why take space away from the Air Force?

The argument for a new military arm rests on the notion that Air Force brass focus their budgets — and priorities — on conventional air superiority, and manage space as only an ancillary theatre of conflict. But the Air Force considers space defense as one of its core missions and has had a Space Command since 1982. Air Force officials — and Defense Secretary Jim Mattis — have argued that setting up a separate space branch would add bureaucratic layers and slow down existing research and programmes. A Space Force might cause Congress to pare the Air Force budget, or other parts of Pentagon or overall spending, to help pay for the new branch. The Air Force gets more than $11 billion for its space programmes — the bulk of the Defense Department’s unclassified national security space programmes, according to the Pentagon’s fiscal 2019 budget request.

What would the force mean for NASA?

It wouldn’t cut into its budget, according to NASA’s new administrator, Jim Bridenstine, who addressed that topic in a July interview with Bloomberg News. And the civilian space agency would still lead the way in space exploration and scientific endeavours.

What would a Space Force do?

The US military doesn’t want to provide specifics, but is working on ways to protect satellites from threats like jamming, blinding sensors by pointing lasers at them, and destruction by “kinetic” objects, such as missiles or other satellites. The US Air Force has a top-secret aircraft, the X-37B, that has orbited Earth for expanded periods; its military purpose is unknown. And Congress’s proposed Defense Authorization Act mandates that the Defense Department come up with a “space warfighting policy”; some lawmakers have called for the military to return to the “Star Wars” ideas and develop weapons that could destroy ballistic missiles from space. On a more workaday level, the Space Command currently tracks the world’s active satellites to make sure they don’t collide with one another or with space debris, and it notifies owners to reposition their satellites if it anticipates an impact.

Would US have offensive space arms?

Probably. The 1967 United Nations Outer Space Treaty, which bans weapons of mass destruction in space, prohibited orbiting nuclear weapons. But it didn’t prohibit other weapons. In an interview with Bloomberg in October, the head of the Air Force Space Command, General John W. “Jay” Raymond, said, “Our goal is not to have conflict in space.” But, he added, space is “a war-fighting domain and we need to treat it as such.”

When would the Space Force start?

Congress would need to authorise it first, something it declined to do last year. With Trump fully on board, the prospects for a sixth service branch — joining the Army, Navy, Air Force, Marines and Coast Guard — could change. Even before a congressional decision, there are reports that the Defense Department is already laying the groundwork to create a Space Force.

Do other countries have space forces?

Yes. Russia created its Aerospace Forces in 2015. China’s space programme was always part of its military; in 2015 the People’s Liberation Army added a Strategic Support Force in part to coordinate all the military’s space-related capabilities.